Re: [PATCH] Powerpc eSDHC: Use u64 to calculate the timeout value to avoid overflow

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On Mon, Nov 12, 2012 at 12:45:28PM +0800, Haijun Zhang wrote:
> As some mmc cards need large timeout value usually a few seconds,
> so data timeout nanosecond will overflow with u32 variable and
> give the wrong timeout value, so use u64 will be safe.
> 
> Signed-off-by: Jerry Huang <Chang-Ming.Huang@xxxxxxxxxxxxx>
> Signed-off-by: Haijun Zhang <Haijun.Zhang@xxxxxxxxxxxxx>
> CC: Anton Vorontsov <cbouatmailru@xxxxxxxxx>
> ---
>  drivers/mmc/core/core.c  |   21 ++++++++-------------
>  drivers/mmc/host/sdhci.c |    6 +++---
>  include/linux/mmc/core.h |    2 +-
>  3 files changed, 12 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 06c42cf..c241fc1 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -208,10 +208,10 @@ mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
>  
>  	if (mrq->data) {
>  		pr_debug("%s:     blksz %d blocks %d flags %08x "
> -			"tsac %d ms nsac %d\n",
> +			"tsac %lld ms nsac %d\n",
>  			mmc_hostname(host), mrq->data->blksz,
>  			mrq->data->blocks, mrq->data->flags,
> -			mrq->data->timeout_ns / 1000000,
> +			div_u64(mrq->data->timeout_ns, 1000000),
>  			mrq->data->timeout_clks);
>  	}
>  
> @@ -659,16 +659,16 @@ void mmc_set_data_timeout(struct mmc_data *data, const struct mmc_card *card)
>  	if (data->flags & MMC_DATA_WRITE)
>  		mult <<= card->csd.r2w_factor;
>  
> -	data->timeout_ns = card->csd.tacc_ns * mult;
> +	data->timeout_ns = (u64)card->csd.tacc_ns * (u64)mult;

one cast would be enough.

>  	data->timeout_clks = card->csd.tacc_clks * mult;
>  
>  	/*
>  	 * SD cards also have an upper limit on the timeout.
>  	 */
>  	if (mmc_card_sd(card)) {
> -		unsigned int timeout_us, limit_us;
> +		u64 timeout_us, limit_us;
>  
> -		timeout_us = data->timeout_ns / 1000;
> +		timeout_us = div_u64(data->timeout_ns, 1000);
>  		if (mmc_host_clk_rate(card->host))
>  			timeout_us += data->timeout_clks * 1000 /
>  				(mmc_host_clk_rate(card->host) / 1000);
> @@ -1545,14 +1545,9 @@ static unsigned int mmc_mmc_erase_timeout(struct mmc_card *card,
>  		/* CSD Erase Group Size uses write timeout */
>  		unsigned int mult = (10 << card->csd.r2w_factor);
>  		unsigned int timeout_clks = card->csd.tacc_clks * mult;
> -		unsigned int timeout_us;
> -
> -		/* Avoid overflow: e.g. tacc_ns=80000000 mult=1280 */
> -		if (card->csd.tacc_ns < 1000000)
> -			timeout_us = (card->csd.tacc_ns * mult) / 1000;
> -		else
> -			timeout_us = (card->csd.tacc_ns / 1000) * mult;
> +		u64 timeout_us;
>  
> +		timeout_us = (u64)(card->csd.tacc_ns / 1000) * (u64)mult;

Ditto.

Otherwise it looks good.

Thanks,
Anton.
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